Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-based compensation awards
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum			21.50%	22.10%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum			33.00%	33.00%
Share-based Compensation, Stock Options, Activity [Table Text Block]			nine
Stock-based compensation expense, before tax (in dollars)	$ 52	$ 48	$ 164	$ 165
Assumptions used in determining the fair value of the stock-based awards
Weighted-average dividend yield (as a percent)			2.70%	3.42%
Weighted-average volatility (as a percent)			30.20%	29.20%
Risk-free interest rates, low end of range (as a percent)			2.02%	0.81%
Risk-free interest rates, high end of range (as a percent)			2.87%	2.35%
Weighted-average expected lives (in years)			8 years	8 years
Unrecognized compensation cost related to nonvested stock-based compensation awards (in dollars)	$ 217		$ 217
Term of amortization of unrecognized compensation cost over weighted-average remaining requisite service periods (in years)			1 year 11 months
Stock Options
Stock-based compensation awards
Shares Granted (in shares)			1,605,220	2,701,644
Weighted-Average Fair Value Per Share (in dollars per share)			$ 46.11	$ 25.01
Weighted-Average Grant Date Stock Price (in dollars per share)	$ 150.90	$ 95.66	150.90	95.66
RSUs
Stock-based compensation awards
Weighted-Average Grant Date Stock Price (in dollars per share)	150.64	96.01	$ 150.64	$ 96.01
Shares Granted (in shares)			722,521	924,421
Weighted-Average Fair Value Per Share (in dollars per share)			$ 150.64	$ 90.11
PRSUs
Stock-based compensation awards
Weighted-Average Grant Date Stock Price (in dollars per share)	$ 150.93	$ 95.66	$ 150.93	$ 95.66
Shares Granted (in shares)			344,866	437,385
Weighted-Average Fair Value Per Share (in dollars per share)			$ 150.93	$ 86.78

The stock price per share on the grant date for issuance to employees under the plan.

No definition available.

Name:	cat_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDatePricePerShare
Namespace Prefix:	cat_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901